Usage of @JsonSerialize and JsonSerializer

Problem

I have a Spring MVC application that requires me to translate the id's and names of a list of a certain entity to an array of JSON objects with specific formatting, and output that on a certain request. That is, I need an array of JSON objects like this:

{
     label: Subject.getId()
     value: Subject.getName()
}

For easy use with the jQuery Autocomplete plugin.

So in my controller, I wrote the following:

@RequestMapping(value = "/autocomplete.json", method = RequestMethod.GET)
@JsonSerialize(contentUsing=SubjectAutocompleteSerializer.class)
public @ResponseBody List<Subject> autocompleteJson() {
    return Subject.findAllSubjects();
}

// Internal class
public class SubjectAutocompleteSerializer extends JsonSerializer<Subject> {

    @Override
    public void serialize(Subject value, JsonGenerator jgen, SerializerProvider provider)
            throws IOException, JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeStringField("label", value.getId().toString());
        jgen.writeStringField("value", value.getName());
        jgen.writeEndObject();
    }
    
}

The JSON I get back however, is the default serialization inferred by Jackson. My custom serializer seems to be completely ignored. Obviously the problem is incorrect usage of @JsonSerialize or JsonSerializer, but I could not find proper usage of these within context anywhere.

Question

What is the proper way to use Jackson to achieve the serialization I want? Please note that it's important that the entities are only serialized this way in this context, and open to other serialization elsewhere